(a) Field of the Invention
The present invention relates to an adapter for the optical connector for connecting optical fibers and, in particular, to an adapter for the optical connector comprising a pair of adapter elements which face to each other and a sleeve holder having an alignment sleeve therein, which is disposed between the adapter elements and a panel fitting for securing the adapter to a panel for wiring optical fibers of communication lines by a single operation.
(b) Description of Related Art
Optical connectors are adapted to connect optical fibers by positioning the optical fibers in the center of cylindrical ferrules and inserting the ferrules into a hollow cylindrical alignment sleeve having precisely manufactured inner diameter to abut the terminal of the ferrule on the terminal of the other ferrule.
The alignment sleeve has been heretofore loosely fitted in a pair of sleeve holders which are identical in shape. The sleeve holders are not press fitted or not bonded to each other, but may be slightly moved independently of each other and is loosely fitted in a pair of housings. The housings are secured to each other by various methods such as screwing,caulking, ultrasonic welding to form an adapter for the optical connector. Examples of the securing methods are as follows:
FIGS. 29(a) and 29(b) show an adapter for the optical connector which connects a pair of optical fibers by conventional screwing. The adapter 10 has a pair of housings 11. Each housing 11 has a flange 11a adjacent to the abut face thereof. The flange 11a of one housing 11 is formed with a screw through-hole and the flange 11a of the other housing 11 is formed with a threaded hole. Both housings are fastened to each other by two screws 12. A sleeve holder 13 is loosely fitted in each of tile housings 11. An alignment sleeve 14 extends through a pair of the sleeve holder 13. The alignment sleeve 14 is formed with a fine slit(not shown) which extends in an axial direction. The ferrules of the plugs which are attached to the terminals of the optical fibers inserted into the alignment sleeve 14 from the opposite sides thereof.
A clearance 15 is provided between the sleeve holders 13 and the alignment sleeve 14. Accordingly, even if the ferrules are inserted into the alignment sleeve 13 in a misalignment manner, the alignment sleeve 14 can bring two ferrules into an alignment relation within the clearance 15.
A reinforcing member (not shown) which is called as plug housing is generally provided along the periphery of the ferrule in order to prevent the misalignment of the ferrules from occurring in the above mentioned adapter. Even if a torsional force which is normal to the axis of the plug is applied to the plug, the force could be absorbed by the pair of housings 11 to some extent. Even if a force which is larger to tilt the ferrules is applied, the alignment sleeve 14 and the ferrules could be correspondingly displaced within the clearance 15. This maintains the contact between the terminals of the optical fibers so that any losses of light will not take place.
The above mentioned adapter 10 for the optical connector can be mounted on an external device such as a panel P for wiring optical fibers of communication lines and the like by means of screws which are screwed into screw holes best shown in FIG. 29(a) where screws 12 are not shown.
FIGS. 30(a) and 30(b) show an adapter for the optical connector for connecting a pair of optical fibers which is assembled by conventional caulking. The adapter 20 includes a pair of housings 21. Each housing 21 has a flange 21a adjacent to the abut face which abuts on the abut face of the other housing 21. The flange 21a of each housing 21 is formed with a through-hole 21b through which a caulking ring extends. As shown in FIGS. 31(a) and 31(b ), a spot facing 21c is formed in the vicinity of the exit of the caulking ring through-hole 21b. The caulking ring 22 has a flange at only one end as shown in FIGS. 32(a) and 32(b).
The caulking ring 22 which is shown in FIGS. 32(a) and 32(b) is inserted into the aligned caulking ring through-holes 21b of the flanges 21a which abut to each other as shown in FIG. 30(b) and then the ring 22 is caulked. This causes both housings 21 to be fastened to each other.
The sleeve holders 23 and the alignment sleeve 24 are fitted to the pair of housings 21 generally similarly to the sleeve holders 13 and the alignment sleeve 14 shown in FIG. 29(a).
The above mentioned adapter 20 for the optical fiber connector is mounted on a panel by means of panel fitting 25 with springs 25a, which are adapted into the opposite sides of either housing 21.
FIGS. 33(a) to 33(c) show an adapter for the optical connector which is assembled by ultrasonic welding. The adapter 30 has a pair of housings 31. Each housing 31 has flanges 31a adjacent to the abut face which abuts on face of the other housing 31. The flanges 31a of each housing 31 are formed with screw through holes 31b to which screws are inserted for securing the adapter to the panel P. As shown in detail in FIG. 33(c), the abut faces of the flanges 31a are formed with various concaves and convexes which facilitate precision positioning and connection of both housings 31 by ultrasonic welding.
The sleeve holder 33 and the alignment sleeve 34 are substantially identical in structure to the sleeve holders 13 and the alignment sleeve 14 shown in FIGS. 29(a) and 29(b), respectively and are fitted in the pair of housings 31 in the same manner as the holders 13 and the sleeve 14.
The sleeve holders 33 are loosely fitted in the housings 31 and the alignment sleeve 34 is inserted into a pair of sleeve holder so that it extends therethrough. Then, the abut faces of the pair of housings 31 are exposed to ultrasonic waves to be welded.
The adapter 30 is mounted on a panel P by means of screws (not shown) which extend through screw holes 31b which are formed through the flanges 31a of the housing 31.
Other structures for mounting an adapter for the optical connector on an external device such as a panel for wiring optical fibers of communication lines are shown in FIGS. 34(a), 34(b) and FIG. 35.
In FIGS. 34(a) and 34(b), the adapter 40 has engaging recess 41c extending from the upper faces 41a of the housings 41 to the both sides 41b. A panel fitting 42 having an external shape which is complementary to the engaging recess 41c is fitted therein. The panel P is sandwiched between the flanges 41d of the housing 41 and the spring piece 42a of the panel fitting 42 so that the adapter 40 is secured to the panel P.
FIG. 35 shows a panel fitting for securing an adapter to a circuit board type panel P. In other words, in FIGS. 29 to 34, the optical connectors are adapted to connect a pair of optical fibers which are positioned in both sides of the panel P.
In FIG. 35, a pair of optical fibers which are positioned in one side of a panel P are connected by the optical fiber connector.
As shown in the drawing, a panel fitting 46 has an L-shape. An upright portion 46a of the fitting 46 is secured to an adapter 45 by fastening means 47. A base portion 46b is secured to the panel P by screwing or soldering.
The above mentioned any conventional adapters require a special tool or facility to secure a pair of housings. Some of them require additional parts for securing the adapter.
The adapters which are screwed require screws which are turned by screw drivers. The adapters which are caulked require caulking rings and caulking is carried out by a press and a caulking jig.
Ultrasonic welding requires an expensive ultrasonic wave generator and a positioning jig. In any cases, it takes an extended period of time to complete a housing securing working.
Since the above mentioned prior art adapter requires flange portions which project from the adapter main body, the size of the whole adapter is large and the size of the lateral section which is normal to the axial direction is about 1.5 to 2 times as large as that of the adapter having no flanges.
In the above mentioned any adapters, the pair of housings are secured to each other so that they will not be displaced. Since the pair of sleeve holders in the housings are independent of each other, they are mounted in such a manner that displacement between them may slightly occur.
In a small adapter which can not be provided with a large clearance between the sleeve holders and the alignment sleeve, displacement between the sleeve holders will further narrow the clearance. There is a disadvantage that losses of light may increase even if a small torsional force is applied to the optical connector plug.
Conventional structures for securing such adapters on panels have problems in mounting density. The adapters shown in FIGS. 29 to 34 have flanges for securing a pair of housings. When these adapters are inserted through the panels for mounting, the flanges are brought into an abutment on one side of a panel and are secured thereto by screwing or using panel fittings 25 and 42 shown in FIGS. 30 and 34, respectively. Since the flanges are larger than the panel fittings, the mounting density does not increase. When the conventional adapters as shown in FIG. 35 are to be secured to the panel P, screws holes of flanges are also used for securing it to the panel fitting which is to be mounted on the panel as shown in FIG. 35. In this case, the flanges are large in size, resulting in a large mounting space.